Formation rate of massive clusters (M_cl ≥ 6 10⁴ M_⊙) in FIREbox galaxies using the cluster formation model ‘Gamma’ (left panel), the ‘EB18’ model (middle panel) and the ‘SFRpeak’ model (right panel). A re-weighting factor corresponding to the halo mass of the host galaxy (see Sect. 2.1) is applied to each BBH obtained. Different colours indicate the contribution of galaxies grouped in different bins of stellar mass, with the same bins as those already used in Figure 2. The black solid line shows the mean total formation rate density obtained from 20 different random realisations, and the grey shaded area is the 90% credible interval.